View Full Version : compressor is heating up to the point it blows hose
Team3844
25-03-2015, 19:36
Last year our compressor ran nonstop during matches but we had no problems with blown hoses.
We just started having this problem after weeks of problem free pnematics on our practice bot.
Does anyone have an idea how to dissipate the heat?
Ben Wolsieffer
25-03-2015, 19:38
What do you mean by blown hoses? Did the hose physically fail, or did it disconnect from the compressor?
I've seen this problem several times. Easiest fix is simply putting a fan on the compressor. The extra airflow does wonders.
Last year our compressor ran nonstop during matches but we had no problems with blown hoses.
We just started having this problem after weeks of problem free pnematics on our practice bot.
Does anyone have an idea how to dissipate the heat?
Do you have the plastic hose connected directly to the fitting on the compressor?
PAR_WIG1350
25-03-2015, 19:50
Adding additional metal fittings between the compressor and the plastic tubing has been known to help cool the air as it exits the compressor.
Dunngeon
25-03-2015, 19:56
Last year our compressor ran nonstop during matches but we had no problems with blown hoses.
We just started having this problem after weeks of problem free pnematics on our practice bot.
Does anyone have an idea how to dissipate the heat?
Are you running the VIAIR 90 C? We too had this issue, for the practice bot we switched the compressor to a Thomas 215 which is rated for 100% duty. We retained the 90C for the competition bot because it only needs to run in short bursts.
Chris_Ely
25-03-2015, 19:57
Add more metal fittings between the compressor and the plastic tubing. You can also place one of the large fans from the kit of parts to blow on the compressor to help cool it.
tickspe15
25-03-2015, 19:59
We use a different type of tube coming off the compressor that is rated for higher temperature operation. I believe the tube we use is rated for 200+ degrees Fahrenheit compared to the KOP tubing which is rated for 120ish degrees. We have also experimented with a metal sheathed tube coming off the compressor but higher rated tube seems to work just as well and be much lighter.
Last year in competition we ran our compressor at %100 duty and burnt out 2 compressors over the course of our 100 match season and replaced the tube from the compressor at every event. This year after three events the tubing we use with the higher temperature rating has no visible deformation anywhere on the tube(even in the fitting).
Yes, we had this problem for Ultimate Ascent (our climber was primarily pneumatically powered). We had several hoses aneurism and rupture at the compressor output. By the time we got to the hose, the outrushing air had cooled the hose, so it took us several times (and changing hose batches) before we figured out that the heat was softening the tubing.
As hinted above, the key is dissipating that heat before reaching the first rubber tubing. In our case, we simply moved the pressure switch, stored pressure gauge, and vent plug onto an all-brass "christmas tree" leading away from the compressor, and put the first fitting to rubber tubing at the far end of all this brass. If this hadn't been enough, we probably would have heat-sinked this mass of metal to radiator fins or the robot chassis, and only then gone to a more active (fan) cooling mechanism.
Basic Chemistry / Gas Laws
PV = nRT
It isn't the compressor. compressing air makes it hot, so you have a lot of hot air coming out. The Thomas had a large surface area on the compressor so it dissapated some heat.
put a metal heat exchange on the output of the compressor - put a length of metal tubing on the output of the compressor, then change over to plastic.
It would be nice if someone made an off the shelf radiator with about a foot length of copper tube with fins, with 1/8 NPT fittings.
PAR_WIG1350
25-03-2015, 21:31
Basic Chemistry / Gas Laws
PV = nRT
It isn't the compressor. compressing air makes it hot, so you have a lot of hot air coming out. The Thomas had a large surface area on the compressor so it dissapated some heat.
put a metal heat exchange on the output of the compressor - put a length of metal tubing on the output of the compressor, then change over to plastic.
It would be nice if someone made an off the shelf radiator with about a foot length of copper tube with fins, with 1/8 NPT fittings.
That sounds like overkill. Given that most teams can handle the issue with parts that are already in the system; a 3" fitting with fins should be more than enough to dissipate heat to acceptable levels for the tubing we are using.
Not overkill for us. We keep most of our robots for years serving as showbots. Sometimes they run 8 or 9 hours a day, with small breaks.
We have two arial assist bots and they use a lot of compressed air, and we blow tubes all the time from heat fatigue. I'd pay money for a good heat exchanger.
Most teams don't need that much cooling but there are enough around that could probably use it.
if anyone see one, please post it.
My team, in 2013, found the same problem with the Viair compressor (Yes, I know the compressor in the picture is the Thompson. Midseason, after burning out a compressor, that was what we had left.) , which we solved by using copper tubing off of the compressor. Might have been excessive overkill, but it solved the problem and worked throughout the season.
PAR_WIG1350
25-03-2015, 23:08
Not overkill for us. We keep most of our robots for years serving as showbots. Sometimes they run 8 or 9 hours a day, with small breaks.
We have two arial assist bots and they use a lot of compressed air, and we blow tubes all the time from heat fatigue. I'd pay money for a good heat exchanger.
Most teams don't need that much cooling but there are enough around that could probably use it.
if anyone see one, please post it.
I forgot to account for that scenario:o .
They do make them (http://www.grainger.com/category/air-and-water-aftercoolers/air-compressor-accessories/pneumatics/ecatalog/N-ae5), but they are rather heavy duty for what we are doing, and are not an allowed part under R66, not that that matters for demonstration purposes.
+1 put a fan on it. also the Tomas seems to be a better compressor. contrary to listed stats it put out more air in a given amount of time for us. but it is bigger.
MrForbes
26-03-2015, 00:13
Mount one of the little kop fans on a bracket on the robot , so it blows on the compressor fins . Do not mount it to the compressor. Power the fan with a 20 amp breaker from the PDP. this is all you need to do to keep the compressor cool.
benherms
26-03-2015, 10:43
If you plan to use the standard ~9% Duty Cycle compressor, use one of the previous-gen Victor fans as we (Team 195) did this year, or any standard electronics cooling fan. Point it directly at the heatsync but do not mount it to the compressor for fear of violating "No-modification" rules.
or any standard electronics cooling fan
? Legal
JamesCH95
26-03-2015, 11:09
Mount one of the little kop fans on a bracket on the robot , so it blows on the compressor fins . Do not mount it to the compressor. Power the fan with a 20 amp breaker from the PDP. this is all you need to do to keep the compressor cool.
x2
This has worked very well for us for several years, especially when combined with mounting all of the metal fittings directly to the compressor.
Nate Laverdure
26-03-2015, 11:13
or any standard electronics cooling fan? Legal
I am guessing that Ether wants us to remember that <R18> limits us to fans that were included in the 2015 KOP or FIRST Choice (http://firstchoicebyandymark.com/search?q=fan).
I am convinced that using a 40mm fan to blow air across the head of a VIAIR 90C is the best configuration for 99% of all FRC applications. Just amazing performance.
We use a different type of tube coming off the compressor that is rated for higher temperature operation. I believe the tube we use is rated for 200+ degrees Fahrenheit compared to the KOP tubing which is rated for 120ish degrees. We have also experimented with a metal sheathed tube coming off the compressor but higher rated tube seems to work just as well and be much lighter.
Could you provide a part number/source for this high-temperature-rated tube?
Mschmeh144
26-03-2015, 13:56
the fan idea works great. our 2013 bot has the compressor overheating problem, but after my overhaul on all the bots, I added a small fan mounted above it blowing down on it and it keeps it very cool. haven't had a air leak since.
ArtemusMaximus
26-03-2015, 15:03
Are you running the VIAIR 90 C? We too had this issue, for the practice bot we switched the compressor to a Thomas 215 which is rated for 100% duty. We retained the 90C for the competition bot because it only needs to run in short bursts.
Correction: Thomas 215 may be better in some regards but it definitely is not rated 100%, it's actually rated only @10%/100psi (Link (http://www.gd-thomas.com/workareashowcontent.aspx?id=24872))
Check this last year thread
http://www.chiefdelphi.com/forums/showthread.php?t=129321
To my knowledge only these 3 compressors are 100% duty and FRC legal (at least according to 2014 rules)
Thomas 405ADC38/12
Thomas 415CDC30/12
Viair 250C-IG
See comparison list I compiled last year http://www.chiefdelphi.com/forums/attachment.php?attachmentid=16981&d=1399302557
rich2202
26-03-2015, 15:27
When they say "10% Duty Cycle", over what period of time is the 10%? 2.5 minutes on (for a match), and 22 minutes off?
We use a different type of tube coming off the compressor that is rated for higher temperature operation. I believe the tube we use is rated for 200+ degrees Fahrenheit compared to the KOP tubing which is rated for 120ish degrees. We have also experimented with a metal sheathed tube coming off the compressor but higher rated tube seems to work just as well and be much lighter.
Don't forget that the pressure relief valve (calibrated to 125 psi or lower) must be connected to the compressor via hard fittings (R67.B, R76). If your compressor only has one port you're going to have at least one tee on it; might as well make it brass and get some heat sink value.
ArtemusMaximus
26-03-2015, 15:48
When they say "10% Duty Cycle", over what period of time is the 10%? 2.5 minutes on (for a match), and 22 minutes off?
Compressor doesn't just work 2.5 minutes on the field. I don't know any team that would let their bot to go on the field with empty stomach .. uh .... I mean empty air tanks. Then it has to work during match. Times between matches are sometimes less than 20-30 minutes. Some of the times is used to adjust bot system and running tests, meaning more compressor usage. No wonder that number of teams have compressor overheating issues.
You cannot call it 100% duty cycle. Besides being incorrect, it is very misleading.
Comparing apples to apples, Viair 90C is 9% Duty cycle, just 1% less than Thomas 215. Which means that difference is marginal.
Having even small fan cooling off compressor will make more impact than switching from Viair 90C to Thomas 215. Especially considering that Thomas 215 is 3 times more expensive that Viair 90C. If you can spare 4 pounds on you robot Viair 250C-IG is much better choice for less money.
AdamHeard
26-03-2015, 16:01
Compressor doesn't just work 2.5 minutes on the field. I don't know any team that would let their bot to go on the field with empty stomach .. uh .... I mean empty air tanks. Then it has to work during match. Times between matches are sometimes less than 20-30 minutes. Some of the times is used to adjust bot system and running tests, meaning more compressor usage. No wonder that number of teams have compressor overheating issues.
You cannot call it 100% duty cycle. Besides being incorrect, it is very misleading.
Comparing apples to apples, Viair 90C is 9% Duty cycle, just 1% less than Thomas 215. Which means that difference is marginal.
Having even small fan cooling off compressor will make more impact than switching from Viair 90C to Thomas 215. Especially considering that Thomas 215 is 3 times more expensive that Viair 90C. If you can spare 4 pounds on you robot Viair 250C-IG is much better choice for less money.
Eh, I'm not sure I trust Vair specs NEARLY as much as Thomas specs.
When they say "10% Duty Cycle", over what period of time is the 10%? 2.5 minutes on (for a match), and 22 minutes off?
I don't know what the maximum on time is for the Thomas but somewhere I saw that the Viar was rated for a max on time of 3min. So a ~30 sec initial charge time, a few minutes of rest, 2.5 minutes of cycling on and off during the match and ~30 minutes between matches puts it in its intended duty cycle.
Eh, I'm not sure I trust Vair specs NEARLY as much as Thomas specs.
Personally the fact that Viair rates theirs at 9% makes me trust their specs more and the fact that Thomas rates theirs at 10% makes me suspicious of their specs. Fact is that real world numbers rarely come out so nice so Viair advertising 9% makes me think it is based on actual data determined by real world testing w/o rounding it up to 10% which would look better on the data sheet.
Team3844
26-03-2015, 21:28
Moved all of our metal fittings down to the compressor for the heat sink value today. It fixed the problem with the added help of throwing more ballast to the back of the robot.
We did discover one trick that we did last year without knowing how it helped.
We used a plastic elbow push fitting as the first non metal fitting last year. The extra heavier thermoset housing helped isolate some of the heat before it got to the tubing.
Team3844
26-03-2015, 21:29
Thanks for all the replys. We learned a lot from going through them with the team.
Basic Chemistry / Gas Laws
PV = nRT
Boyle's Law caused us a bit of a search for a leak one year. We filled up the tanks, and a few seconds later, the compressor started again when the air cooled a bit and the pressure dropped.
ArtemusMaximus
27-03-2015, 12:55
I don't know what the maximum on time is for the Thomas but somewhere I saw that the Viar was rated for a max on time of 3min. So a ~30 sec initial charge time, a few minutes of rest, 2.5 minutes of cycling on and off during the match and ~30 minutes between matches puts it in its intended duty cycle.
Personally the fact that Viair rates theirs at 9% makes me trust their specs more and the fact that Thomas rates theirs at 10% makes me suspicious of their specs. Fact is that real world numbers rarely come out so nice so Viair advertising 9% makes me think it is based on actual data determined by real world testing w/o rounding it up to 10% which would look better on the data sheet.
Spec sheet for Thomas states 3 minutes on - 30 minutes off @ 23°C
http://www.gd-thomas.com/workareashowcontent.aspx?id=24872
Al Skierkiewicz
27-03-2015, 13:14
Art,
Can you tell us which compressor you are using?
ArtemusMaximus
27-03-2015, 16:27
Art,
Can you tell us which compressor you are using?
Ah, I am not part of the team this year (few different reasons). So I am not using anything this year. Last year we were using only standard equipment that came in a tote (Viair 90C). But I did a research last year and if you remember you contributed to this thread http://www.chiefdelphi.com/forums/showthread.php?t=129321. If i'd be still on the team I would insist to use VIAIR 250C-IG. It just make sense to me :)
In this thread I stepped in to address the statement that Thomas 215 had 100% duty cycle, which I knew was incorrect.
Al Skierkiewicz
28-03-2015, 08:58
Art,
Sorry, I was speaking to the OP, Arthur Canada.
There seems to be four compressors that everyone is using these days.
The original Thomas 415 which is heavy but a great work horse. (Top and side ports are legal)
The Viair 90C (The top port is not legal for FRC and the nickel plated check valve must be in place.)
Viair 250 (The included stainless steel hose must be attached for FRC rules)
Thomas 215 (the top and side ports are both legal to use and this compressor does not require an external check valve)
The two small compressor run very hot as there is little thermal mass to absorb the heat generated. External cooling can be applied provided no modification to the compressor is made. (Do not use the screws to mount other devices.)
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